PCF v4

A living spec for building with an AI coding agent.

PCF v4 carries a product's full context (problem, brand, data model, build order) through one file that an agent reads from and writes to at every stage, so nothing has to be re-explained the next time you sit down to work.

Context resets constantly

Building a real product with an AI coding agent involves dozens of decisions. The problem being solved, who it's for, the brand, the data model, the tech stack, the build order, all made across many separate sessions.

Without a single persistent record, that context resets every time. The same questions get re-answered, decisions get re-litigated, and the plan quietly drifts from what's actually being built.

PCF v4 solves this with one living PROJECT.md that the agent reads from and writes to at every stage: discovery, brand, system design, build planning, QA, deployment. The project's full context and decision history stays in one place automatically.

One file, read and written at every stage

PROJECT.md lives in the project's own repo, never inside the framework itself. Each phase (Discovery, Brand, System Design, Build Plan, QA, Deployment) reads what's already there, adds its section, and updates a Status block at the top. The next session, whether it's hours or weeks later, picks up exactly where the last one left off.

  1. Idea
  2. PROJECT.md created
  3. Phase 1–12, read + written in sequence
  4. Shipped product
## Status
Phase: 4 (Brand), complete
Last updated: 2026-07-06

## 4. Brand
### Personality
Calm, disciplined, quietly opinionated

A trimmed excerpt of this exact page's own PROJECT.md. The Status block is what every session reads first to know where to resume.

What a phase actually looks like

This section is a real, lightly-trimmed excerpt from this very page's ownPROJECT.md. This site was built using PCF v4 itself.

## 7. System Design
### Tech Stack

- Framework: Astro. Ships zero JS by default, built for content
  and marketing pages, far less config overhead than Next.js for
  a single-page site.
- Styling: Tailwind CSS v4. Pairs directly with the @theme tokens
  already defined in Phase 4.
- Hosting: Cloudflare Pages. Static output, free tier, deploys
  from git push.

Rejected alternative: Next.js. Capable, but adds SSR/routing/
server-component complexity not needed for one static page.

Setup time estimate: about 1 to 2 hours.

One phase, confirmed with the user, written to the file. Then the next phase starts from a project that already has this decision on record.

Not tied to one tool

PROJECT.md is a plain file. Any agent that can read and edit files can run PCF v4 against it: Claude Code, OpenCode, or any other file-reading, file-writing agent. None of them is the "main" one. The framework's logic lives in the file and the instructions, not in any particular product.